Thomas Whalan is a member of a select group of Australian water polo players who have played at four Olympic Games. He made his Olympic debut at the Sydney 2000 Games where he was the youngest Australian player on the team, which finished in eighth position. The outside shooter then competed at Athens 2004, finishing ninth, and Beijing 2008, finishing eighth. Whalan married Olympic swimmer Elka Graham just after the Beijing Games.
At the London 2012 Games and after losing three of their first four matches, the Australians knocked off Greece 13-8 to book a spot in the quarter-finals against Serbia. The Aussies took a 7-4 halftime lead before going down 8-11 to the eventual bronze medallists. Whalan finished with eight goals in the competition.